Erythroderma‐like crusted scabies in an immunocompetent patient after systemical corticosteroids

Dear Editor,

Crusted (Norwegian) scabies are a severe and rare form of scabies typically observed in immunocompromised patients, characterized by extensive scabbing, scaling, and hyperkeratosis. ¹ However, the occurrence of erythroderma in patients with scabies is quite uncommon, accounting for less than 0.5% of cases. ² Erythroderma is a condition defined by skin inflammation, which is frequently caused by pre‐existing chronic skin conditions such as psoriasis, eczema, infections, or drug reactions. ³ Notably, treating these underlying causes can sometimes be contradictory, and administering unsuitable treatment may worsen the original skin disease. Since erythrodermic crusted scabies are relatively rare, it is crucial to promptly recognize and manage the condition.

Ten months ago, a 78‐year‐old Chinese woman presented with pruritus and red maculopapular on her abdomen. The rash progressively worsened, leading to multiple hospital visits where she was diagnosed with “senile pruritus, eczema, and hypereosinophilic dermatitis.” She was given oral antihistamines and topical corticosteroid hormones. However, the severity of the condition varied. The patient underwent systemic corticosteroid treatment for a duration of 2 months. However, the rash continued to spread all over her body, leading to worsened pruritus and sleep disturbance. Patients visited our clinic and underwent a physical examination. Examination revealed diffuse erythroderma with yellow scales on the scalp, trunk, arms, and legs (Figure 1). Additionally, the finger suture areas exhibited thick, crusted plaques with fissures and a focal powdery scale (Figure 2). Dermoscopy identified the presence of a white tunnel with a jet‐like appearance, along with a brown mini triangular scabies mite head positioned at one end of the tunnel (Figure 3). The diagnosis of scabies mite was further confirmed under a microscope (Figure 4). These findings established the diagnosis of erythrodermic scabies. The patient was treated with four courses of 200 µg/kg ivermectin, with each course separated by 1 week. Additionally, the patient applied sulfur ointment to her entire body once daily after bathing for 3 days. After 4 weeks of initiating therapy, her disseminated erythema had resolved, and the pruritus had ceased.

FIGURE 1.

Clinical presentation: diffuse erythroderma with white‐grayish scale on the trunk, arms, and legs.

FIGURE 2.

Clinical presentation: thick crusted plaques with fissures and focal powdery scale.

FIGURE 3.

Dermoscopy showed white tunnel with a jet‐like appearance with brown mini triangular scabies mite heads at the end of tunnel.

FIGURE 4.

The microscopic examination of a skin scraping revealed a Sarcoptes scabiei mite.

Research indicates that the topical application of high concentrations of corticosteroids can result in widespread psoriasiform lesions or erythroderma in patients with scabies. ⁴ Immunodeficiency or sensory deficits are risk factors for erythrodermic scabies. The patient in our case study exhibited normal immune function, had no medical history of conditions such as AIDS or autoimmune diseases, and had no known allergies to food, drugs, or other substances. Erythroderma‐like presentation developed after the administration of systemic corticosteroids. She was diagnosed with erythrodermic scabies by dermoscopy and microscopy.

Erythrodermic scabies, a rare form of crusted scabies, primarily affects immunocompromised individuals, rendering their immune system ineffective against scabies mites in the skin, which results in a severe infestation of thousands to millions of mites. ⁵ Erythrodermic scabies are easily misdiagnosed as other diseases with erythrodermic appearance. Accurate diagnosis of scabies depends on dermoscopy and microscopy. ⁴ In addition, the ball sign observed under UV dermoscopy is helpful for the diagnosis of scabies, ⁶ The reflective confocal microscope and the typical skin CT are helpful in the diagnosis and differentiation of scabies. ⁷

Corticosteroids are extensively utilized for treating skin diseases due to their established efficacy as immunosuppressive and anti‐inflammatory drugs. However, it is important to acknowledge that the use of corticosteroids could occasionally lead to the development of new lesions during the treatment process. This case report suggests that scabies should also be considered when the rash worsens in patients treated with corticosteroids. This case highlights the significance of accurately diagnosing scabies as the underlying cause of erythroderma, as doing so helps avoid the potentially harmful effects of misdiagnosis and inappropriate treatment.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.